Keio University Transistor Computer K-1

Keio University Transistor Computer K-1

Keio University Transistor Computer K-1


Logic package

Logic package


Magnetic drum

Magnetic drum



Manufactured in 1959
Manufactured by Department of Electric Engineering, Faculty of Engineering, Keio University
Owner Faculty of Science and Technology, Keio University
Location of historical materials K-1 CPU is exhibited in the first basement of Building 11 and the drum is done in the first basement of Buil 11th Building, Yagami Campus, Keio University,
3-14-1 Hiyoshi, Kohoku-ku, Yokohama-shi, Kanagawa-ken, 223-8552 Japan
Visitor information Open to the public (Reservation required)
Contact Tel.+81-45-566-1454


Keio University developed the transistor computer K-1 in 1958 as a part of the project celebrating the university's centennial anniversary. Based on ETL Mark IV transistor computer of the Electrnotechnical Laboratory (ETL), they developed a fully transistorized machine. To meet the need for scientific and engineering computation, a floating point arithmetic unit and index registers were introduced. They adopted dynamic circuits for basic circuits. The clock was synchronous and the rate was 200kHz.

Internally, the K-1 was decimal-based and used the bit-parallel/digit-serial system. The word length was expanded from 6 digits to 12 digits. A high speed magnetic drum was used as an internal memory. As for input/output devices, a mechanical tape reader, a Flexowriter, and a paper tape punch were used.

Misao Kitagawa and Togo Tsuzuki of Faculty of Engineering engaged in the design work of ETL Mark V at ETL and studied the practical work of computer design. After finishing the study at ETL, they returned to Keio University in July 1958 and started to design the K-1 transistor computer. From November 1958, Kitagawa, Tsuzuki and the students of the laboratory began to fabricate the K-1 and then tested the machine. The machine test was completed in June 1959 and the K-1 began to operate. Thus the first Japanese university made transistor computer was born.

In July 1961, the computer center was established within the Faculty of Engineering, K-1 was installed there and was used until 1968 for the research and education within the campus.

Currently the central processing unit (CPU) of K-1 and a magnetic drum are preserved in Yagami Campus of Keio University. The CPU is exhibited in the basement of 11th Building and the drum is in the basement of 14th Building.